Pyrazolate copper complexes, and MOCVD of copper using same

ABSTRACT

Copper pyrazolate precursor compositions useful for the formation of copper in semiconductor integrated circuits, e.g., interconnect metallization in semiconductor device structures, as an adhesive seed layer for plating, for the deposition of a thin-film recording head and for circuitization of packaging components. The copper pyrazolate precursor compositions include fluorinated and non-fluorinated pyrazolate copper (I) complexes and their Lewis base adducts. Such precursors are usefully employed for liquid delivery chemical vapor deposition of copper or copper-containing material on a substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to copper precursor compositionsand their synthesis, and to a method for production of copper circuitsin microelectronic device structures, as for example in formation ofmetal interconnects for the manufacture of semiconductor integratedcircuits, thin-film recording heads and packaging components, orotherwise for metallizing or forming copper-containing films on asubstrate by metalorganic chemical vapor deposition (MOCVD) utilizingsuch precursor compositions. The precursor compositions of the inventionare also usefully employed for forming seed layers of copper forsubsequent electroless or electrochemical plating of copper and othermetals.

[0003] 2. Description of the Related Art

[0004] As a result of its low resistivity, low contact resistance, andability to enhance device performance through the reduction of RC timedelays, copper has emerged as a preferred metal for metallization ofVLSI devices. Copper metallization has been adopted by manysemiconductor device manufacturers for production of microelectronicchips, thin-film recording heads and packaging components.

[0005] Chemical vapor deposition (CVD) of copper provides uniformcoverage for the metallization. Liquid CVD precursors and/or solidprecursors dissolved into solvents or excess ligands enable directinjection and/or the liquid delivery of precursors into a CVD vaporizerunit. The accurate and precise delivery rate can be obtained throughvolumetric metering to achieve reproducibility during CVD metallizationof a VLSI device.

[0006] Currently only a few liquid copper precursors are commerciallyavailable. These include (hfac)Cu(MHY), (hfac)Cu(3-hexyne),(hfac)Cu(DMCOD) and (hfac)Cu(VTMS), whereinhfac=1,1,1,5,5,5-hexafluoroacetylacetonato, MHY=2-methyl-1-hexen-3-yne,DMCOD=dimethylcyclooctadiene, and VTMS=vinyltrimethylsilane.

[0007] Various copper precursors useful for MOCVD of copperinterconnects in semiconductor integrated circuits are described in U.S.Pat. Nos. 5,085,731; 5,098,516; 5,144,049; and 5,322,712; and thereferences cited in those patents. New and useful compositions andprocesses for the production of copper that improve on, or providealternatives to, these known compositions would be highly desirable andembody a significant advance in the art.

[0008] With respect to the copper precursors that have come into use forcopper MOCVD metallization, there are concerns associated with using(hfac)CuL precursors, where hfac=1,1,1,5,5,5-hexafluoroacetylacetonateand L=neutral Lewis base ligands. Copper metallization in integratedcircuit manufacture typically utilizes a barrier layer between thecopper layer and the underlying structure in order to preventdetrimental effects that may be caused by the interaction of a copperlayer with other portions of the integrated circuit. A wide range ofbarrier materials is conventionally utilized, including materialscomprising metals, metal nitrides, metal suicides, and metal siliconnitrides. Exemplary barrier materials include titanium nitride, titaniumsilicide, tantalum nitride, tantalum silicide, tantalum siliconnitrides, niobium nitrides, niobium silicon nitrides, tungsten nitride,and tungsten silicide. In instances where (hfac)CuL type precursors areused for copper metallization, interfacial layers are formed between thebarrier layer and the copper layer. These interfacial layers cause themetallization to have poor adhesion and high contact resistivity.

[0009] The deficiencies of inferior adhesion and excessively highcontact resistivity incident to formation of interfacial layers whenusing (hfac)CuL copper precursors has been attributed to the hfacligand, which contains both oxygen and fluorine. To overcome suchdeficiencies, it would be a significant advance in the art to providecopper MOCVD precursors having a reduced oxy/fluoro content. It would beparticularly advantageous to provide copper MOCVD precursors of anoxygen-free character.

[0010] It is accordingly an object of the present invention to provide anew class of anoxic (oxygen-free) copper precursors and formulations.

[0011] It is another object of the invention to provide methods offorming copper in the manufacturing of integrated circuits and othermicroelectronic device structures using such precursors andformulations.

[0012] It is a further object of the invention to provide metallizationtechnology for forming interconnects and other device structures thatovercome the shortcomings and limitations of the prior art, includingimproved adhesion, improved contact resistances, improved filmresistivities and improved device integration.

[0013] It is another object of the invention to provide a method ofmetallizing or forming copper-containing films on a substrate bymetalorganic chemical vapor deposition (MOCVD) utilizing such novelcopper precursor compositions and formulations.

[0014] It is a further object of the invention to provide adherentthin-films for seeding electroless and/or electrochemical platingsolutions and to overcome the shortcomings and limitations of the priorart, including improved adhesion, improved contact resistances, improvedfilms resistivities, improved plating, improved conformality, improvedmanufacturing, and improved device integration.

[0015] Other objects and advantages of the present invention will bemore fully apparent from the ensuing disclosure and appended claims.

SUMMARY OF THE INVENTION

[0016] The present invention relates generally to copper pyrazolatecompositions, which are advantageously of an oxygen-free character,useful as source reagents for forming copper on substrates, and tomethods of making and using such compositions.

[0017] In one aspect, the invention relates to a composition useful forthe production of copper by chemical vapor deposition, comprising one ormore pyrazolate copper (I) Lewis base adduct(s).

[0018] In a particular aspect, the invention relates to a copperprecursor of the formula (RR′R″)PzCuL, wherein (RR′R″)Pz is a pyrazolylmoiety of the formula:

[0019] wherein R, R′ and R″ are independently the same as or differentfrom one another and each of R, R′ and R″ is independently selected fromH, C₆-C₁₀ aryl, C₆-C₁₀ fluoroaryl, C₁-C₆ alkyl, C₁-C₆ fluoroalkyl, C₁-C₆perfluoroalkyl, and C₃-C₆ cycloalkyl, with the proviso that at least oneR contains fluorine; and L is a neutral Lewis base ligand, such as aneutral Lewis base alkene, alkyne or diene.

[0020] A further aspect of the invention relates to pyrazolate copper(I) Lewis base adducts that are devoid of oxygen constituents therein.

[0021] Another aspect of the invention relates to specific copperprecursor formulations useful for liquid delivery metalorganic chemicalvapor deposition of copper, comprising:

[0022] (a) a precursor composition selected from the group consistingof:

[0023] (i) pyrazolate copper (I) compounds; and

[0024] (ii) pyrazolate copper (I) neutral Lewis base adducts; and

[0025] (b) a solvent composition for the precursor composition.

[0026] A further aspect of the invention relates to copper precursorformulations useful for liquid delivery metalorganic chemical vapordeposition of copper, comprising:

[0027] (a) a precursor composition selected from the group consistingof:

[0028] (i) (RR′R″)PzCu wherein: Pz is a pyrazolyl moiety and R, R′ andR″ are independently the same as or different from one another and eachof R, R′ and R″ is independently selected from H, C₆-C₁₀ aryl, C₆-C₁₀fluoroaryl, C₁-C₆ alkyl, C₁-C₆ fluoroalkyl, C₁-C₆ perfluoroalkyl, andC₃-C₆ cycloalkyl;

[0029] (ii) (RR′R″)PzCuL wherein: Pz is a pyrazolyl moiety and R, R′ andR″ are independently the same as or different from one another and eachof R, R′ and R″ is independently selected from H, C₆-C₁₀ aryl, C₆-C₁₀fluoroaryl, C₁-C₆ alkyl, C₁-C₆ fluoroalkyl, C₁-C₆ perfluoroalkyl, andC₃-C₆ cycloalkyl, with the proviso that at least one R containsfluorine; and L is a Lewis base ligand, such as an amine or a neutralLewis base alkene, alkyne, or diene; and

[0030] (b) a solvent composition for the precursor composition.

[0031] A further aspect of the invention relates to pyrazolate copper(I) precursor formulations that are devoid of oxygen constituentstherein.

[0032] Another aspect of the invention relates to specific copperprecursors such as [(CF₃)₂PzCu]₃, (CF₃)₂PzCu(3-hexyne), and(CF₃)₂PzCu[bis(tms)acetylene], wherein Pz is a pyrazolyl moiety and tmsis trimethylsilyl.

[0033] In further aspects, the invention variously relates to: a processuseful for the production of copper, in which a composition of theabove-described type is subjected to chemical vapor deposition; aprocess of forming a seed layer by liquid injection or directvaporization of a composition of the above-described type; copper madeby the process of subjecting to chemical vapor deposition a compositionof such type; and integrated circuits made using such process.

[0034] A further aspect of the invention relates to a process forsynthesizing a copper precursor, including reacting (RR′R″)pyrazolestarting material with a stoichiometric excess of Cu₂O, and recovering(R,R′R″)pyrazolyl copper from the reaction, optionally followed byreacting the (R,R′R″)pyrazolyl copper with a neutral Lewis basecompound, to yield a (R,R′R″)pyrazolyl copper Lewis base adduct. TheLewis base adducted pyrazolate copper complexes exhibit highersolubility in organic solvents. Such high solubility is particularlyadvantageous in making solution compositions using the solid complexes.

[0035] A still further aspect of the invention relates to a process forsynthesizing a copper precursor, including reactingbis(trifluoromethyl)pyrazole with a stoichiometric excess of Cu₂O, andrecovering bis(trifluoromethyl)pyrazolyl copper from the reaction,optionally followed by reacting the bis(trifluoromethyl)pyrazolyl copperwith a neutral Lewis base compound, to yield abis(trifluoromethyl)pyrazolyl copper Lewis base adduct. Another aspectof the invention relates to a process for synthesizing the(RR′R″)pyrazolyl copper Lewis base adduct directly from the Lewis basein the presence of Cu₂O and (RR′R″)pyrazole starting material.

[0036] Yet another aspect of the invention relates to a method ofdepositing copper on a substrate, comprising volatilizing a copperprecursor composition of the present invention, to form a precursorvapor and contacting the precursor vapor with the substrate underelevated temperature vapor decomposition conditions to deposit copper onthe substrate.

[0037] The precursor compositions of the invention are useful for themanufacture of copper, including copper interconnects for integratedcircuits, thin-film recording heads and/or packaging components.

[0038] Other aspects and features of the invention will be more fullyapparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 is a schematic representation of a liquid delivery andvaporization system as may be used with a chemical vapor deposition(CVD) chamber for the deposition of copper-containing material on asubstrate in accordance with the present invention.

[0040]FIG. 2 schematically shows a portion of an exemplary IC withinterconnects and an integral capacitor that may be fabricated inaccordance with the invention.

[0041]FIG. 3 is an STA thermal analysis plot for [(CF₃)₂PzCu]₃.

[0042]FIG. 4 is an STA thermal analysis plot for3,5-bis(trifluoromethyl)pyrazole.

[0043]FIG. 5 is an STA thermal analysis plot for (CF₃)₂PzCu(3-hexyne).

[0044]FIG. 6 is an STA thermal analysis plot for(CF₃)₂PzCu[bis(tms)acetylene].

[0045]FIG. 7 is an Ortep representation of3,5-(CF₃)₂PzCu[bis(tms)acetylene].

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

[0046] The disclosures of the following United States patents and patentapplications are hereby incorporated herein by reference in theirentireties:

[0047] U.S. patent application Ser. No. 08/835,768 filed Apr. 8, 1997 inthe names of Thomas H. Baum, et al.;

[0048] U.S. patent application Ser. No. 08/484,654 filed Jun. 7, 1995 inthe names of Robin A. Gardiner et al.;

[0049] U.S. patent application Ser. No. 08/414,504 filed Mar. 31, 1995in the names of Robin A. Gardiner et al.;

[0050] U.S. patent application Ser. No. 08/280,143 filed Jul. 25, 1994,in the names of Peter S. Kirlin, et al.;

[0051] U.S. patent application Ser. No. 07/927,134, filed Aug. 7, 1992in the same names;

[0052] U.S. patent application Ser. No. 07/807,807, filed Dec. 13, 1991in the names of Peter S. Kirlin, et al., now issued as U.S. Pat. No.5,204,314;

[0053] U.S. application Ser. No. 08/181,800 filed Jan. 15, 1994 in thenames of Peter S. Kirlin, et al., and issued as U.S. Pat. No. 5,453,494;

[0054] U.S. application Ser. No. 07/918,141 filed Jul. 22, 1992 in thenames of Peter S. Kirlin, et al., and issued Jan. 18, 1994 as U.S. Pat.No. 5,280,012;

[0055] U.S. application Ser. No. 07/615,303 filed Nov. 19, 1990;

[0056] U.S. application Ser. No. 07/581,631 filed Sep. 12, 1990 in thenames of Peter S. Kirlin, et al., and issued Jul. 6, 1993 as U.S. Pat.No. 5,225,561; and

[0057] U.S. patent application Ser. No. 07/549,389 filed Jul. 6, 1990 inthe names of Peter S. Kirlin, et al.

[0058] The oxygen-free pyrazolate copper compositions of the presentinvention are based on the discovery that3,5-bis(trifluoromethyl)pyrazole may be used, instead of the (hfac)Hligand species that have been used to make prior art (hfac)CuL copperprecursors, to produce useful precursors for MOCVD of copper.

[0059] The copper source reagents of the invention include pyrazolatecopper (I) compounds, and pyrazolate copper (I) Lewis base adducts.

[0060] The pyrazolate copper (I) compounds of the invention includecopper precursors of the formula [(RR′R″)PzCu]₃ wherein: Pz is apyrazolyl moiety and R, R′ and R″ are independently the same as ordifferent from one another and each of R, R′ and R″ is independentlyselected from H, C₆-C₁₀ aryl, C₆-C₁₀ fluoroaryl, C₁-C₆ alkyl, C₁-C₆fluoroalkyl, C₁-C₆ perfluoroalkyl, and C₃-C₆ cycloalkyl.

[0061] The pyrazolate copper (I) Lewis base adducts of the inventioninclude copper precursors of the formula (RR′R″)PzCuL wherein: Pz is apyrazolyl moiety and R, R′ and R″ are independently the same as ordifferent from one another and each of R, R′ and R″ is independentlyselected from H, C₆-C₁₀ aryl, C₆-C₁₀ fluoroaryl, C₁-C₆ alkyl, C₁-C₆fluoroalkyl, C₁-C₆ perfluoroalkyl, and C₃-C₆ cycloalkyl, with theproviso that at least one R contains fluorine; and L is a Lewis baseligand, for example a neutral Lewis base alkene, alkyne or diene, suchas those deriving from compounds of the following formulae:

[0062] wherein R₁, R₂, R₃ or R₄ may be the same as or different from oneanother, and are independently selected from H, aryl, fluoroaryl,perfluoroaryl, C₁-C₈ alkyl or open-chain alkyl, C₁-C₈ fluoroalkyl, C₁-C₈perfluoroalkyl, alkene, alkyne, ketones and cyclic versions of theaforementioned groups

[0063] (II) alkynes of the formula:

R₂—≡—R₁

[0064] wherein R₁ and R₂ may be the same or different and areindependently selected from H, aryl, fluoroaryl, C₁-C₈, perfluoroaryl,C₁-C₈ alkyl, C₁-C₈ fluoroalkyl, C₁-C₈ perfluoroalkyl, vinyl, C₅-C₆cycloalkyl, alkene, alkyne, ketone and cyclic versions of theaforementioned groups; and

[0065] (III) dienes of the formula:

[0066] wherein R₁ R₂, R₃, R₄, R₅ and R₆ may be the same or different andare independently selected from H, and C₁-C₃ alkyl and wherein n=0, 1,2, 3 or 4.

[0067] Pyrazolate copper (I) Lewis base adducts L of the invention mayalso be formed with amines as coordinated ligand species. Amine adductsmay be formed for example by complexation of a pyrazolate copper (I)compound with an amine in a solvent composition comprising an aminesolvent component. Preferred amine Lewis base ligand species L useful inthe invention include primary, secondary and tertiary amines. Morepreferably, the amine Lewis base ligand species (L) may includetriethylamine, tetramethylethylenediamine, tributylamine andtripropylamine.

[0068] Other useful Lewis base ligand species L include 1-hexene,vinyltrimethylsilane, 2-hexyne, 3-hexyne, 2-butyne,5-vinyl-2-norbornene, 1,5-dimethylcyclooctadiene,2-methyl-1-hexen-3-yne, 2,5-dimethyl-2,4-hexadiene,bis(trimethylsilyl)acetylene, dipentene, 1-pentene, 1-butene, 1-propene,isoprene, trimethylphosphine, triethylphosphine, dimethyl sulfide anddiethyl sulfide.

[0069] Particularly preferred adduct species of the invention includepyrazolate copper (I) Lewis base adducts that are devoid of oxygenconstituents therein.

[0070] More generally, the copper source reagent compounds and complexesof the invention may be of any suitable character consistent with thediscussion herein. Illustrative copper precursors such as [(CF₃)₂PzCu]₃,(CF₃)₂PzCu(3-hexyne), and (CF₃)₂PzCu[bis(tms)acetylene], wherein Pz is apyrazolyl moiety and tms is trimethylsilyl, e.g., (CH₃)₃Si—, are morefully described hereinafter, but it will be recognized that the presentinvention is broadly applicable to encompass a wide variety offluorinated and non-fluorinated pyrazolate copper (I) complexes andtheir Lewis base adducts, as well as the use of such complexes andadducts in a wide variety of end uses involving the formation of copperfor specific end uses and applications, including copper metallizationof integrated circuitry and microelectronic device structures, formationof plating base seed layers, etc.

[0071] The invention also relates to a process for synthesizing thecopper pyrazolate precursors, by reacting (RR′R″)pyrazole with astoichiometric excess of Cu₂O, preferably in a suitable solvent medium,such as an alkane, substituted alkanes, aryl, or substituted arylsolvent, and recovering (RR′R″)pyrazolyl copper from the reactionvolume, to provide a copper reagent that may itself be used in copperMOCVD, as well as being amenable to the formation of adducted species byreacting the (RR′R″)pyrazolyl copper with a Lewis base compound, toyield a (RR′R″)pyrazolyl copper Lewis base adduct. The adduct speciesare particularly useful in liquid delivery MOCVD processes to formcopper, by delivering the composition to a process tool through use of aliquid delivery system. The adduct species may be delivered to the CVDprocess either neat or in solution. In some cases excess Lewis baseligand may be added to the solution composition or the Lewis base ligandmay be used as the solvent.

[0072] The invention also relates to a process for synthesizing thecopper pyrazolate precursors, by reacting bis(trifluoromethyl)pyrazolewith a stoichiometric excess of Cu₂O, preferably in a suitable solventmedium, such as an alkane, haloalkane, aryl, or haloaryl solvent, andforming bis(trifluoromethyl)pyrazolyl copper from the reaction volume,to provide a copper reagent that may itself be used in copper MOCVD, aswell as being amenable to the formation of adducted species by reactingthe bis(trifluoromethyl)pyrazolyl copper with a Lewis base compound, toyield a bis(trifluoromethyl)pyrazolyl copper Lewis base adduct.

[0073] In CVD usage, the copper precursor of the invention isvolatilized to form a precursor vapor that then is contacted with asubstrate under elevated temperature vapor decomposition conditions todeposit copper on the substrate.

[0074] As a specific synthesis method, the copper pyrazolatecompositions of the present invention are readily synthesized byreacting 3,5-bis(trifluoromethyl)pyrazole with an excess amount of Cu₂Oin a suitable solvent medium such as CH₂Cl₂ optionally in the presenceof L (=neutral Lewis base ligand species), as shown in reaction equation1 below, wherein Pz=pyrazolyl and wherein n is zero or 1.

H[Pz(CF₃)₂]+Cu₂O+nL→(CF₃)₂PzCuL_(n)+H₂O  (1)

[0075] When n is zero, the synthesis is carried out in the absence ofany L ligand species, to form [(CF₃)₂PzCu]₃ by reacting3,5-bis(trifluoromethyl)pyrazole with an excess amount of Cu₂O in thesolvent, e.g., CH₂Cl₂ solvent.

[0076] Upon the completion of the reaction, the excess amount of Cu₂Omay be removed by filtration, e.g., by filtering the reaction mixturethrough Celite® or other filtration media, followed by removal of thesolvent, e.g., under vacuum from the filtrate.

[0077] When no ligand L is present in the reaction mixture,[(CF₃)₂PzCu]₃ is obtained as a solid. Unlike [(hfac)Cu]_(n),[(CF₃)₂PzCu]₃ is very stable, exhibiting no decomposition even up to240° C. This affords direct purification of the copper complex prior toLewis base adduct formation. By contrast the polymeric species of[(hfac)Cu]_(n) undergoes a disproportionational reaction even at −50°C., forming Cu metal and Cu(hfac)₂.

[0078] [(CF₃)₂PzCu]₃ is volatile and thermally stable, and is usefullyemployed as a Cu MOCVD precursor under reducing ambient depositionconditions in the CVD reactor. The solid precursor can dissolve inorganic solvents, and liquid delivery can be used to meter the solutioninto a vaporizer for transport to the reactor.

[0079] In the CVD reactor, in a hydrogen atmosphere, the reduction asexpressed in equation 2 takes place to produce elemental copper, Cu(0).

(CF₃)₂PzCu+H₂ _(⁻) →(CF₃)₂PzH+Cu(0)  (2)

[0080] (CF₃)₂PzH is the only by-product formed during the MOCVD processwhen (CF₃)₂PzCu is used as a precursor. As a result of its volatilityand stability, as depicted by FIG. 4, (CF₃)₂PzH can be easily removedfrom the growing film and the CVD reactor.

[0081] Complexes of the formula (CF₃)₂PzCu(L) are readily formed bycarrying out the reaction of equation (1), involving reaction of3,5-bis(trifluoromethyl)pyrazole with an excess amount of Cu₂O in thesolvent medium, together with the ligand species L in the reactionvolume. The resultant adducted complexes exhibit increased solubility inorganic solvents and are particularly useful in liquid delivery CVDprocesses.

[0082] The ligand species L may be any suitable neutral Lewis basespecies, e.g., alkene, alkyne, diene, ene-yne, ene-one, diyne, keto-ene,keto-yne or cyclic versions of the aforementioned species, etc. Specificexamples of useful Lewis base species include 1-hexene, isoprene,vinyltrimethylsilane, 2-hexyne, 3-hexyne, 2-butyne,5-vinyl-2-norbornene, 2,5-dimethyl-2,4-hexadiene,1,5-dimethylcyclooctadiene, 2-methyl-1-hexen-3-yne,bis(tri-methylsilyl)acetylene, 1-pentene, 1-butene, 1-propene anddipentene. Any suitable amines may also be used as a ligand species L.

[0083] The solvent medium used for the synthesis of [(CF₃)₂PzCu]₃ orLewis base complexed adducts thereof may be any suitable solvent speciesor mixture of solvents appropriate to support the reaction. Examples ofuseful solvents include dichloromethane, trichloromethane,trichloroethane, butane, pentane, hexane, heptane, octane, toluene,dimethylformamide, and other alkane, aryl, amine and halocarbonsolvents. In some cases the Lewis base ligand may be used as the solventor as a constituent of the solvent mixture.

[0084] The present invention thus provides novel copper pyrazolatecomplexes using as copper MOCVD precursors. The copper pyrazolatecomplexes of the invention afford significant advantages over (hfac)CuLcomplexes, since they are non-oxygen containing, thermally stable,volatile and much less air-sensitive than prior art (hfac)CuL complexes.

[0085] The copper pyrazolate complexes of the invention may also besynthesized using corresponding non-halogenated or less-halogenatedpyrazoles in place of 3,5-bis(trifluoromethyl)pyrazole for reaction withCu₂O. Rather than the trifluoromethyl substituents on the pyrazoleillustratively described hereinabove, corresponding pyrazole analogs maybe employed with one or both of the trifluoromethyl substituents beingalkyl or otherwise non-fluoro in character.

[0086] The invention therefore contemplates fluorinated andnon-fluorinated pyrazolate copper (I) complexes and their Lewis baseadducts for use as copper CVD precursors.

[0087] The invention correspondingly relates to a CVD process that usesthese precursor materials, e.g., in the form of neat liquid precursors,as well as in solution compositions containing copper precursors of theinvention in compatible solvent media, for copper metallization or theformation of copper seed layer via either liquid injection or directvaporization.

[0088] More specifically, and by way of example, the copper pyrazolateprecursor compositions of the present invention may be used during theformation of copper interconnect lines in semiconductor integratedcircuitry, thin-film circuitry, thin-film packaging components andthin-film recording head coils. To form such integrated circuitry orthin-film circuitry, a semiconductor substrate may be utilized having anumber of dielectric and conductive layers (multilayers) formed onand/or within the substrate. The semiconductor substrate may include abare substrate or any number of constituent layers formed on a baresubstrate.

[0089] In the broad practice of the present invention, acopper-containing layer may be formed on a semiconductor substrate usingthe copper pyrazolate precursor, for use in a first, second, third, ormore metallization layer. Such copper layers typically are used incircuit locations requiring low resistivity, high performance and/orhigh speed circuit paths. As discussed in the background section hereof,before a copper layer is formed on a semiconductor substrate, a barrierlayer may be deposited or otherwise formed on the substrate.

[0090] Using the copper precursor compositions described herein, coppermay then be deposited on the wafer using a CVD system. Metalorganic CVD(MOCVD) systems may be utilized for such purpose, such systems beingwell known in the semiconductor fabrication art. MOCVD systemspotentially useful in the broad practice of the invention includeatmospheric pressure MOCVD systems as well as low (or reduced) pressureMOCVD systems.

[0091] The precursor compositions of the present invention are notlimited in respect of their use with such deposition tools, however, andother CVD tools, for example PECVD tools, or other deposition tools, maybe utilized. Further, water, water-generating compounds, or otheradjuvants to the precursor formulation may be mixed with the copperprecursor upstream of, or within, the CVD tool. Similarly, reducingagents may be utilized in an analogous fashion.

[0092] As a further variation, when copper alloy compositions are to bedeposited on the substrate, the copper precursor formulation may containor be mixed with other metal source reagent materials, or such otherreagent materials may be separately vaporized and introduced to thedeposition chamber.

[0093] The compositions of the present invention may be delivered to aCVD reactor in a variety of ways. For example, a liquid delivery systemmay be utilized. Such systems generally include the use of liquid MFCs(mass flow controllers). An exemplary liquid delivery system useful inthe general practice of the invention is the ADCS Sparta 150 LiquidDelivery System (commercially available from Advanced TechnologyMaterials, Inc., Danbury, Conn.). A combined liquid delivery and flashvaporization process unit may be employed, such as the LDS300 liquiddelivery and vaporizer unit (commercially available from AdvancedTechnology Materials, Inc., Danbury, Conn.), to enable low volatilitymaterials to be volumetrically delivered, leading to reproducibletransport and deposition without thermal decomposition of the precursor.Both of these considerations of reproducible transport and depositionwithout thermal decomposition are essential for providing a commerciallyacceptable copper CVD process.

[0094] Liquid delivery systems generally meter a desired volumetricquantity of a liquid or solution to achieve a uniform flow rate of theprecursor composition to the CVD process tool. At the process toolchamber the liquid may be vaporized through use of a vaporizer or atransducer activated by ultrasound or acoustic techniques. Variousconfigurations and types of liquid delivery systems are described inU.S. Pat. Nos. 5,204,314; 5,362,328; 5,536,323; and 5,711,816, thedisclosures of which are hereby expressly incorporated herein byreference in their entireties.

[0095] In liquid delivery formulations, copper precursor complexes andadducts that are liquids may be used in neat liquid form, or liquid orsolid copper complexes and adducts may be employed in solventformulations containing same. Thus, copper precursor formulations of theinvention may include solvent component(s) of suitable character as maybe desirable and advantageous in a given end use application to formcopper on a substrate. Suitable solvents may for example include alkanesolvents, e.g., hexane, heptane, octane, pentane, or aryl solvents suchas benzene or toluene, amines and amides, as well as other alkane, aryland halocarbon solvents. The utility of specific solvent compositionsfor particular copper precursor complexes and adducts may be readilyempirically determined, to select an appropriate single component ormultiple component solvent medium for the liquid delivery vaporizationand transport of the specific copper precursor employed. It is generallydesirable to avoid oxo (—O—) solvents such as ethers as solvent speciesin the copper precursor formulations of the invention.

[0096] The use of the compositions disclosed herein is not limited toliquid delivery systems, and any method that adequately delivers theprecursor composition to the process may be usefully employed. Thus, forexample, bubbler-based delivery systems may be utilized. In suchsystems, an inert carrier gas may be bubbled through the precursorcomposition to provide a resulting gas, which is wholly or partiallysaturated with the vapor of the precursor composition, for flow to theCVD tool.

[0097] A wide variety of CVD process conditions may be utilized with theprecursor compositions of the present invention. Generalized processconditions may include substrate temperature ranges of 150-400° C.;pressure ranges of 0.05-5 Torr; and carrier gas flows of helium,hydrogen, nitrogen, or argon at 25-750 sccm at a temperatureapproximately the same as the vaporizer.

[0098] The copper pyrazolate precursor compositions of the inventionalso have utility for the deposition of plating base layers, e.g., byliquid delivery CVD techniques, to achieve reproducible delivery,reproducible film growth and uniform deposition rates in the depositionof thin conductive films (e.g., having a thickness on the order of 1000Angstroms).

[0099] The deposition of copper thin films with useful electricalproperties (low resistivity) and good adhesion to the barrier layer(e.g., formed of TiN or TaN), are also achieved by the process andprecursors of the present invention. The conformality of the depositedfilm is practically achievable only through CVD techniques that therebyprovide a pathway to the achievement of “full-fill” coppermetallization. The liquid delivery approach of the present invention,including “flash” vaporization and the use of copper precursor chemistryas herein disclosed, enable next-generation device geometries anddimensions to be attained, e.g., a conformal vertical interconnect of0.13 micron linewidths with 4-8:1 aspect ratio. The conformal depositionof interconnects of these critical dimensions cannot be realized bycurrently available physical deposition methods. Thus, the approach ofthe present invention affords a viable pathway to future generationdevices, and embodies a substantial advance in the art.

[0100]FIG. 1 is a schematic representation of a liquid delivery MOCVDsystem 100 that may be employed in the practice of the invention formetallization in the manufacture of semiconductor devices, or otherwisefor forming a copper-containing material on a substrate, using a liquidsource reagent.

[0101] The delivery system 100 includes a first fluid feed passage 10into which a first fluid is introduced in the direction indicated byarrow F₁. The first fluid may comprise a carrier gas, such as argon, aswell as other gaseous components, e.g., source compounds, additives,co-reactants, reducing agents or other species.

[0102] The first fluid feed passage 10 is connected to a gasdistribution manifold at its proximal end 11, and is open at its distalend 13. The distal portion 16 of passage 10 is mounted in a housing 12of a reactor, such as a CVD growth chamber. The distal portion 16 of thefirst fluid feed passage 10 thus is centrally disposed in thecylindrical portion 15 of the CVD reactor 12, to form an annularinterior volume 17 therebetween.

[0103] Communicating with the annular interior volume 17 is a secondfluid flow passage 18, into which second fluid is introduced in thedirection indicated by arrow F₂, through the open end 19 of the passage.The second fluid introduced in passage 18 to the reactor may includeother source reagent materials, or components or carrier gas species,such as hydrogen, nitrogen, argon, etc.

[0104] Disposed in the proximal portion 21 of the first fluid flowpassage 10 is a flash vaporization matrix structure 26, which is joinedin liquid delivery relationship by conduit 28 and conduit 32, havingcheck valve 30 therebetween, to liquid reservoir 34. The liquidreservoir 34 may contain one or more copper pyrazolate precursors inaccordance with the invention. If the particular copper pyrazolateprecursor complex is of a solid form, the liquid reservoir 34 may beconstructed and arranged to hold a solution comprising the copperpyrazolate precursor and a suitable solvent medium therefor, or if thecopper pyrazolate precursor is a suitable liquid, then the reagentalone.

[0105] The copper pyrazolate precursor species if of solid form atambient conditions is suitably dissolved or suspended in a compatiblesolvent medium, as more fully described in U.S. Pat. No. 5,820,664issued Oct. 13, 1998 for “PRECURSOR COMPOSITIONS FOR CHEMICAL VAPORDEPOSITION, AND LIGAND EXCHANGE RESISTANT METAL-ORGANIC PRECURSORSOLUTIONS COMPRISING SAME,” the disclosure of which is herebyincorporated herein in its entirety by reference.

[0106] Conduit 28 is sized and arranged (mounted on flash vaporizationmatrix structure 26) in such manner as to prevent premature evaporationof any volatile components (e.g., solvent constituents) of the sourceliquid that is flowed through conduit 28 to the vaporization matrixstructure for flash vaporization thereon. The conduit 28 extends throughlateral extension 20 of first fluid flow passage 10.

[0107] The delivery system 100 shown in FIG. 1 comprises a vaporizationzone 22, which may be maintained at a suitable elevated temperaturecommensurate with the flash vaporization of reagent source liquid on theflash vaporization matrix structure 26.

[0108] Downstream from the vaporization zone 22 is an injection zone 24,wherein a second fluid is introduced via second fluid flow passage 18.The injection zone 24 is maintained at a suitable temperature, which maybe somewhat less than the temperature of the vaporization zone,depending on the various constituents introduced through the respectivefirst and second fluid flow feed passages. In some instances of thepresent invention, it may be advantageous to introduce a copperprecursor by injection via the injection zone.

[0109] In operation, the first fluid is flowed in the direction F₁,through first fluid flow passage 10 into the reactor 12, beingdischarged at the distal open end 13 of the first fluid flow passage 10.Concurrently with such flow of gas therethrough, the reagent sourceliquid from reservoir 34 is flowed through conduit 32, check valve 30,and conduit 28, to the flash vaporization matrix structure 26.

[0110] The flash vaporization matrix structure 26 may be formed of anysuitable material which does not deleteriously interact with the reagentsource liquid or other fluid species introduced into the first fluidflow passage. The matrix structure should also be heatable to sufficientelevated temperature to effect flash vaporization of the reagent sourceliquid that is introduced from conduit 28 onto the surfaces of thematrix structure. The matrix structure may for example be formed ofmetals such as stainless steel, copper, silver, nickel, iridium,platinum, etc., as well as ceramics, high temperature glasses, quartz,chemically treated quartz, composite materials, and the like, the choiceof a specific material of construction being dependent on thetemperature regime which is encountered by the matrix structure, as wellas the composition of the reagent source liquid and fluid flowed pastthe structure in the first fluid flow passage 10. Preferably, the matrixstructure is constructed of an inert metal, and has a relatively highsurface-to-volume ratio, as for example at least about 4, morepreferably at least about 10, and most preferably at least about 100,when the surface and volume are measured in corresponding area andvolume dimensional units (viz., square and cubic values of the samedimensional units). Preferably the matrix structure is foraminous (i.e.,porous or perforate) in character.

[0111] The flash vaporization matrix structure may take the form of ascreen, porous sintered material body, grid, or the like. Thecomposition, surface area, and surface-to-volume characteristics of thematrix structure are selected so as to effect flash vaporization of thereagent source liquid on the surfaces of the structure, nearcontemporaneously with application of liquid thereon.

[0112] The conduit 28 introducing the reagent source liquid onto thematrix structure 26 may simply be an open-ended tube, i.e., a tube whoseopen end communicates with the matrix structure, whereby liquid issuingfrom the conduit flows onto the surfaces of the matrix structure forflash vaporization thereon, when the grid is heated to suitable elevatedtemperature. As previously discussed, conduit 28 is appropriately sizedand arranged relative to the vaporization matrix structure 26 to preventany undesirable premature evaporation of the reagent source liquidbefore the flash vaporization thereof on the matrix structure.

[0113] In order to enhance the dispersion and distribution of reagentsolution onto the surfaces of the matrix structure, the conduit 28 mayhave a restriction rod (not shown) centrally disposed therein to form aninterior annular conduit, whereby pressure drop in the conduit isadjusted to a desired level, and whereby liquid appropriately issues ina thin film onto the matrix structure surfaces. Alternatively, theconduit 28 may be joined to a suitable nozzle or distributor means (notshown) at the distal end of the conduit, to facilitate distribution ofsource reagent liquid onto the matrix structure surfaces.

[0114] The source reagent solution reservoir 34 may be associated orotherwise coupled with a suitable liquid pumping means (not shown), suchas a positive displacement liquid pump which effects discharge ofreagent source liquid from the reservoir through conduit 32, check valve30, and conduit 28 to the matrix structure 26. The reagent source liquidmay be introduced onto the vaporization matrix structure in a steadystream injection mode or in a pulsed injection mode from the conduit 28.In general, steady stream injection of the reagent source liquid isdesirable in CVD applications since it provides the most stableconcentration of the source reagent in the downstream reactor, however,pulsed injection of the reagent source liquid may be advantageous insome applications.

[0115] Preferably, the matrix structure 26 is formed of a material ofconstruction having a high specific heat capacity, so that the structureis substantially unaffected by heat of vaporization effects, whereby thematrix structure is suitably maintained at a desirable elevatedtemperature for continuous operation and vaporization of the reagentsource liquid. Materials of construction which may contaminate thedeposited films sought to be formed from the source reagent liquid,e.g., iron, should be avoided in the practice of the invention, inapplications where the composition and stoichiometry of the depositedcopper-containing film are critical.

[0116] The check valve 30 between conduits 28 and 32 controls the on/offflow of reagent source liquid therethrough to the matrix structure 26and is required to prevent the uncontrolled delivery of the sourcereagent solution to the matrix structure 26 under reduced pressureoperating conditions.

[0117] The reagent source liquid delivered to the heated matrixstructure 26 is vaporized and then carried by a first fluid (carriergas) into the deposition reaction chamber 12 for deposit of acopper-containing material on a substrate therein. The first fluid mayalso comprise other reagents from various upstream bubblers or othersource means therefor.

[0118]FIG. 2 schematically shows a portion of an exemplary IC with anintegral capacitor that may be fabricated in accordance with theinvention. The illustrated portion of integrated circuit 201 includes afirst active device 210, such as a conventionalmetal-oxide-semiconductor field effect transistor (MOSFET), and acapacitor 205 employing a dielectric film layer of (Ba,Sr) titanateformed on a substrate 215, such as a silicon substrate. A drain regionof a second transistor 220 is also shown. The particular types of activedevices employed, e.g., NMOS, PMOS or CMOS, are based on the desiredoperation of the integrated circuit and are not critical for practicingthe present invention. Other suitable active devices include, forexample, bipolar junction transistors and GaAs MESFETs.

[0119] The transistors 210 and 220 can be fabricated, for example, byconventional processing methods. In FIG. 2, the transistors 210 and 220include field oxide regions 225 and 230 that are formed, for example, bySiO₂ and operate as insulators between the transistor 210 and adjacentdevices, such as the transistor 220. Source and drain regions 235 and240 of the transistor 210 are formed by doping with n-type impurities,such as arsenic or phosphorus for NMOS. An optional layer of silicide245 is deposited over the source and drain regions 235 and 240 to reducethe source and drain resistance, which enables greater current deliveryby the transistor 210.

[0120] A gate 250 of the transistor 210 includes, for example,polysilicon 255 doped with an n-type impurity, such as by an implant orvapor doping. The gate polysilicon 255 is disposed on a SiO₂ spacer 260.An optional layer of silicide 262 is also deposited over the gatepolysilicon 255 to reduce the electrical resistance of the gate 250. Aninsulating layer 265 of, for example, P-glass which is an oxide dopedwith phosphorus, is then deposited on the transistors 210 and 220 toprovide protection to the transistors 210 and 220 and to facilitateelectrical connection. Contract windows 266 are then etched in theinsulating layer 265 to expose the device gate 250 and source and drainregions, such as the regions 235 and 240. Although only the drainregions of the transistors 210 and 220 are exposed in the cross-sectionof the integrated circuit illustrated in FIG. 2, it should be readilyunderstood that the gate and source are exposed at other areas of theintegrated circuit 1 that are outside the illustrated cross-section.

[0121] The capacitor 205 includes a first electrode 270 formed on theinsulating layer surface, a dielectric thin film region 275 on the firstelectrode 270, and a second electrode 280 formed on the dielectric filmregion 275 opposite the first electrode 270. It is possible for thefirst electrode 270 to have a two-layer structure. Such a structure is,for example, a layer of platinum formed over a layer of Ti-nitride orTiAlN. Platinum alone is not a suitable electrode material, however,since it adversely chemically reacts with silicon. As a consequence, adiffusion barrier is advantageously employed as the second electrodelayer which is in contact with the insulating layer surface, tosubstantially prevent a chemical reaction between the platinum and thesilicon of the substrate 215. Suitable thicknesses for each layer of thetwo-layer structure are in the range of 0.01 to 0.5 μm.

[0122] It is further possible for the first electrode 270 to be a singlelayer structure of an appropriate conductive material. Overall suitablethicknesses for the first electrode 270, whether a one or two layerstructure, are in the range of approximately 0.1 to 0.5 μm. Thicknessesless than 0.1 μm are undesirable because of its high electricalresistance while thicknesses greater than 0.5 μm are generallydisadvantageous because of high fabrication cost and poor adherence. Thefirst electrode 270 is larger than the second electrode 280 to provideelectrical connection to the first electrode 270.

[0123] After formation of the capacitor 205, an insulating material 285,such as, for example, SiO₂ is deposited on edge regions 290, 291 and 292of the capacitor 205 to prevent short circuits between the first andsecond capacitor electrodes 270 and 280 when the interconnection layeris formed. A copper interconnection layer 295 is then formed on theinsulation layer and corresponding etched contact windows toelectrically connect the devices 210 and 220 and the capacitor 205, byCVD using a copper precursor in accordance with the present invention.In the integrated circuit 201, the drain 240 of the transistor 210 iselectrically connected to the first electrode 270 of the capacitor 280and the capacitor's second electrode 280 is electrically connected tothe source of the transistor 220.

[0124] The features and advantages of the invention are more fullyapparent from the following non-limiting examples.

EXAMPLE 1

[0125] [(CF₃)₂PzCu]₃ was synthesized by reacting3,5-bis(trifluoromethyl)pyrazole with an excess amount of Cu₂O in CH₂Cl₂solvent. Upon the completion of the reaction, the excess amount of Cu₂Owas filtered through Celite®. Removal of the solvent under vacuo fromthe filtrate gave a white solid. An STA thermal analysis plot for[(CF₃)₂PzCu]₃ is shown in FIG. 3 and evidences a melting endotherm peakat 208° C. and complete transport below 240° C. without significantdecomposition (residue).

EXAMPLE 2

[0126] An STA thermal analysis was conducted for (CF₃)₂PzH to determinethe properties of such by-product of copper MOCVD when [(CF₃)₂PzCu]₃ isused as a precursor and the CVD process is conducted under reducingconditions using a hydrogen atmosphere.

[0127] The corresponding STA thermal analysis plot for (CF₃)₂PzH isshown in FIG. 4 and shows that the onset of transport begins at 90° C.,and was completed below 140° C. at atmospheric pressure.

EXAMPLE 3

[0128] (CF₃)₂PzCu(3-hexyne) was synthesized by reacting (CF₃)₂PzH withan excess amount of Cu₂O in the presence of 3-hexyne in CH₂Cl₂. Afterthe reaction was completed, the mixture was filtered, and a colorlessfiltrate was obtained. Removal of volatiles under vacuum gave whitesolid product. ¹H NMR study revealed that it was (CF₃)₂PzCu(3-hexyne).Thermal analysis (see the FIG. 5 STA thermal analysis plot) indicatedthe compound lost the alkyne Lewis base ligand around 110° C. After thedissociation of the alkyne ligand, a melting endotherm appeared at 208°C., indicative of the formation of the trimeric [(CF₃)₂PzCu]₃ thattransports intact below 240° C.

EXAMPLE 4

[0129] [(CF₃)₂PzCu]₃ was mixed with bis(tms)acetylene in CH₂Cl₂. After 5hours, removal of volatiles gave an off-white solid. The solid wasfurther purified by recrystallization in n-pentane. Pale yellow crystalswere obtained. ¹H NMR study revealed that this compound was(CF₃)₂PzCu[bis(tms)acetylene]. Thermal analysis, shown in the FIG. 6 STAthermal analysis plot, revealed that the compound lost the alkyne ligandaround 124° C., forming a material with a melting point at 208° C.,indicative of the formation of trimeric [(CF₃)₂PzCu]₃. This Lewis baseligand does not prevent liquid delivery and efficient vaporization.

[0130] Single crystal X-ray diffraction studies revealed that(CF₃)₂PzCu[bis(tms)acetylene] was a dimer, having the formula reflectedin the FIG. 7 Ortep representation of the molecular structure.

[0131] While the invention has been described herein with reference tospecific features and illustrative embodiments, it will be recognizedthat the utility of the invention is not thus limited, but ratherextends to and encompasses other features, modifications and alternativeembodiments as will readily suggest themselves to those of ordinaryskill in the art based on the disclosure and illustrative teachingsherein. The claims that follow are therefore to be construed andinterpreted as including all such features, modifications andalternative embodiments within their spirit and scope.

What is claimed is:
 12. A copper precursor formulation, comprising: aprecursor composition selected from the group consisting of: pyrazolatecopper (I) compounds of the formula [(RR′R″)PzCu]₃ wherein: Pz is apyrazolyl moiety and R, R′ and R″ are independently the same as ordifferent from one another and each of R′ and R″ is independentlyselected from H, C₆-C₁₀ aryl, C₆-C₁₀ fluoroaryl, C₁-C₆ alkyl, C₁-C₆fluoroalkyl, C₁-C₆ perfluoroalkyl, C₆-C₁₀ perfluoroaryl and C₃-C₆cycloalkyl, with the proviso that at least one R contains fluorine; andpyrazolate copper (I) Lewis base adducts of the formula (RR′R″)PzCuLwherein: Pz is a pyrazolyl moiety and R, R′ and R″ are independently thesame as or different from one another and each of R′ and R″ isindependently selected from H, C₆-C₁₀ aryl, C₆-C₁₀ fluoroaryl, C₁-C₆alkyl, C₁-C₆ fluoroalkyl, C₁-C₆ perfluoroalkyl, C₆-C₁₀ perfluoroaryl andC₃-C₆ cycloalkyl, with the proviso that at least one R containsfluorine; and L is a Lewis base ligand; and a solvent composition forthe precursor composition.
 13. A copper precursor formulation accordingto claim 12, wherein said solvent composition comprises an organicsolvent.
 14. A copper precursor formulation according to claim 12,wherein said solvent composition comprises a solvent selected from thegroup consisting of alkane, aryl, amine and halocarbon solvents.
 15. Thecopper precursor formulation according to claim 14, wherein said solventcomposition further comprises a neutral Lewis-base ligand.
 16. Thecopper precursor formulation according to claim 15, wherein said neutralLewis base ligand of the solvent composition and said Lewis-base adductof the precursor composition are the same.
 17. The copper precursorformulation according to claim 12, wherein the solvent compositioncomprises a neutral Lewis-base ligand.
 18. A copper precursorformulation according to claim 12, wherein said solvent compositioncomprises a solvent selected from the group consisting of hexane,heptane, octane, pentane, dichloromethane, trichloromethane,trichloroethane, benzene, toluene, and dimethylformamide.
 19. A copperprecursor formulation according to claim 11, wherein said solventcomposition is substantially free of oxo (—O—) solvents.
 20. A copperprecursor formulation useful for liquid delivery metalorganic chemicalvapor deposition of copper, comprising: a precursor composition selectedfrom the group consisting of: [(RR′R″)PzCu]₃ wherein: Pz is a pyrazolylmoiety and R, R′ and R″ are independently the same as or different fromone another and each of R, R′ and R″ is independently selected from H,C₆-C₁₀ aryl, C₆-C₁₀ fluoroaryl, C₁-C₆ alkyl, C₁-C₆ fluoroalkyl, C₁-C₆perfluoroalkyl, and C₃-C₆ cycloalkyl; and pyrazolate copper (I) Lewisbase adducts; and (RR′R″)PzCuL wherein: Pz is a pyrazolyl moiety and R,R′ and R″ are independently the same as or different from one anotherand each of R, R′ and R″ is independently selected from H, C₆-C₁₀ aryl,C₆-C₁₀ fluoroaryl, C₁-C₆ alkyl, C₁-C₆ fluoroalkyl, C₁-C₆ perfluoroalkyl,and C₃-C₆ cycloalkyl, with the proviso that at least one R containsfluorine; and L is a neutral Lewis base ligand; and a solventcomposition for the precursor composition.